Two-piece magnetic shield having improved heat dissipation

ABSTRACT

Problems such as thermal pole tip protrusion result from thermal mismatch between the alumina and pole material during the writing process. This, and similar problems due to inadequate heat dissipation, have been overcome by dividing the bottom shield into two pieces both of which sit on top of a non-magnetic heat sink. Heat generated by the coil during writing is transferred to the non-magnetic heat sink whence it gets transferred to the substrate. With this approach, the head not only benefits from less field disturbance due to the small shield but also improves heat dissipation from the additional heat sink

FIELD OF THE INVENTION

The invention relates to the general field of magnetic heads with particular reference to dissipating heat in accompanying magnetic shields.

BACKGROUND OF THE INVENTION

For high areal density magnetic recording, one of the requirements is to have lower fly height in order to have better signal to noise ratio for better head performance. However, there are many reliability problems associated with this low fly height. Problems such as thermal pole tip protrusion, resulting from thermal mismatch between the alumina and pole material during the writing process will create a head disk interface problem and eventually damage the read head.

One way to reduce thermal pole tip protrusion is to have a better heat dissipation mechanism so that heat generated by the coil during the writing process can be transferred to the substrate to avoid heat accumulation. On the other hand, it is required to have a small shield that only covers the read sensor (to reduce external field disturbance) in order to improve the overall reader performance. Thus there is a problem of how to make a small active shield have good heat dissipation.

A routine search of the prior art was performed with the following references of interest being found:

In U.S. Pat. No. 6,239,954 Segar et al. disclose a non-magnetic element over the bottom shield to detect and cancel thermal changes in the read head. In U.S. Pat. No. 6,556,389 Boutaghou et al. describe a thermal barrier of zirconia over the magnetic read head element to dissipate heat while Inoue et al. show a AIN heat sink over a bottom shield in US Patent 2002/0081778.

SUMMARY OF THE INVENTION

It has been an object of at least one embodiment of the present invention to provide a magnetic read-write head that is subject to minimum heating during operation.

Another object of at least one embodiment of the present invention has been to provide a magnetic read head that is minimally disturbed by external fields.

Still another object of at least one embodiment of the present invention has been to provide a process for manufacturing said read-write head.

These objects have been achieved by dividing the bottom shield into two pieces both of which sit on top of a non-magnetic heat sink. Heat generated by the coil during a writing process is transferred to the non-magnetic heat sink whence it gets transferred to the substrate. With this approach, the head not only benefits from less field disturbance due to the small shield but also improves heat dissipation from the additional heat sink

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the starting point for the process of the present invention.

FIGS. 2 and 3 show the formation of the heat dissipating underlayer.

FIGS. 4 and 5 illustrate formation of the split magnetic shield.

FIG. 5 shows the completed device, including a double planar writer.

FIGS. 6 and 7 shows the completed device, exemplified as a double planar writer and a low DC resistance writer, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention teaches a novel method to make a two-piece bottom shield with both pieces sitting on top of a non-magnetic metal heat sink. The heat generate by the coil during writing is transferred to the non-magnetic metal heat sink and hence transfers to the substrate. With this approach, the head not only benefits from less field disturbance (due to the small shield) but also receives improved the heat dissipation from the additional heat sink We will disclose the invention through a description of the process for manufacturing a read-write head that includes the key novel features of the invention, namely the split shield underlaid by a heat sink. Said process description will also serve to make clear the structure of the present invention.

Referring now to FIG. 1, the process of the present invention begins with the provision of substrate 11 and then depositing thereon dielectric layer 12. Then layer of non-magnetic material 21, having a thermal conductivity greater than about 300 W/m.K, is deposited onto dielectric layer 12. Layer 21 is then patterned to reduce its area so that the upper surface of layer 12 is exposed on opposite sides of it, as illustrated in FIG. 2. Examples of materials suitable for layer 21 include (but are not limited to) copper and nickel-copper. It is deposited to a thickness between about 1 and 2 microns.

The structure is then fully covered with second dielectric layer 31, following which it is planarized until thermally conductive layer 21 is just exposed, as illustrated in FIG. 3.

Next, ferromagnetic layer 41 is deposited (to a thickness between about 1 and 3 microns) on the structure's upper surface and patterned to form coplanar, opposing magnetic shields 41 a and 41 b, separated by gap 42 that extends as far as the upper surface layer 21. Gap 42 is between about 4 and 10 microns wide.

The structure is then fully covered with dielectric layer 51, following which it is planarized until magnetic shields 41 a and 41 b are just exposed. This completes formation of the lower magnetic shield for a full read-write head. Examples of these are shown in FIGS. 6 and 7. In both cases read head 61 (encapsulated in a dielectric medium) is seen directly above the lower shield. Magnetic read head 61 may be a CIP (current in plane) or a CPP (current perpendicular to plane) design.

Write head 62 is an example of a double planar writer while write head 72 is an example of a LDCR (low DC resistance) writer. In both cases manufacture of the full read-write head concludes by planarizing parallel to plane 63 or 73 to define the air bearing surface (ABS). 

1. A method to improve heat dissipation in a magnetic shield, comprising: providing said shield in the form of a layer of ferromagnetic material on a substrate; inserting a layer of non-magnetic material, having a thermal conductivity greater than about 300 W/m.K, between said shield and said substrate; and splitting said shield into two opposing parts separated by a gap.
 2. The method described in claim 1 wherein said thermally conductive layer of non-magnetic material is selected from the group consisting of Cu and NiCu.
 3. The method described in claim 1 wherein said thermally conductive layer of non-magnetic material is deposited to a thickness between about 1 and 2 microns.
 4. The method described in claim 1 wherein said gap separating said opposing shield parts is between about 4 and 10 microns wide.
 5. A process to form a magnetic shield, comprising: providing a substrate and depositing thereon a first dielectric layer having a first upper surface; onto said first dielectric layer, depositing a layer of a non-magnetic material having a thermal conductivity greater than about 300 W/m.K; patterning said thermally conductive layer so as to expose said first upper surface on opposing sides of said thermally conductive layer; fully covering said thermally conductive layer and said exposed first upper surface with a second dielectric layer and then planarizing until said thermally conductive layer is just exposed, thereby forming a second upper surface; depositing and patterning a ferromagnetic layer on said second upper surface to form coplanar opposing first and second magnetic shields separated by a gap that exposes said second upper surface; and fully covering said magnetic shields and second upper surface with a third dielectric layer and then planarizing until said magnetic shields are just exposed.
 6. The process described in claim 5 wherein said thermally conductive layer of non-magnetic material is selected from the group consisting of Cu and NiCu.
 7. The process described in claim 5 wherein said thermally conductive layer of non-magnetic material is deposited to a thickness between about 1 and 2 microns.
 8. The process described in claim 5 wherein said gap separating said opposing shield parts is between about 4 and 10 microns wide.
 9. The process described in claim 5 wherein said ferromagnetic layer is deposited to a thickness between about 1 and 3 microns.
 10. A process to manufacture a magnetic read/write head, comprising: providing a substrate and depositing thereon a first dielectric layer having a first upper surface; onto said first dielectric layer, depositing a layer of a non-magnetic material having a thermal conductivity greater than about 300 W/m.K; patterning said thermally conductive layer so as to expose said first upper surface on opposing sides of said thermally conductive layer; fully covering said thermally conductive layer and said exposed first upper surface with a second dielectric layer and then planarizing until said thermally conductive layer is just exposed, thereby forming a second upper surface; depositing and patterning a ferromagnetic layer on said second upper surface to form coplanar opposing first and second magnetic shields separated by a gap that exposes said second upper surface; fully covering said magnetic shields and second upper surface with a third dielectric layer and then planarizing until said magnetic shields are just exposed, thereby forming a third upper surface; forming, on said third upper surface, a magnetic read-head that is sandwiched between upper and lower dielectric layers; forming a bottom write-head shield on said upper dielectric layer; forming, on said bottom write-head shield, a magnetic write head having a write gap; and planarizing, in a plane normal to said third upper surface, until said first magnetic shield, said read head, said bottom write-head shield, and said write gap are all exposed.
 11. The process recited in claim 10 wherein said thermally conductive layer of non-magnetic material is selected from the group consisting of Cu and NiCu.
 12. The process recited in claim 10 wherein said thermally conductive layer of non-magnetic material is deposited to a thickness between about 1 and 2 microns.
 13. The process recited in claim 10 wherein said gap separating said opposing shield parts is between about 4 and 10 microns wide.
 14. The process described in claim 10 wherein said ferromagnetic layer is deposited to a thickness between about 1 and 3 microns.
 15. The process described in claim 10 wherein said magnetic read head is a CIP magnetic read head.
 16. The process described in claim 10 wherein said magnetic read head is a CPP magnetic read head.
 17. The process described in claim 10 wherein said magnetic write head is a double planar write head.
 18. The process described in claim 10 wherein said magnetic write head is a Low DC Resistance read head.
 19. A magnetic shield having good heat dissipation, comprising: a layer of ferromagnetic material on a substrate; between said ferromagnetic layer and said substrate, a layer of non-magnetic material, having a thermal conductivity greater than about 300 W/m.K; and said layer of ferromagnetic material further comprising two opposing parts separated by a gap.
 20. The magnetic shield described in claim 19 wherein said thermally conductive layer of non-magnetic material is selected from the group consisting of Cu and NiCu.
 21. The magnetic shield described in claim 19 wherein said thermally conductive layer of non-magnetic material has a thickness between about 1 and 2 microns.
 22. The magnetic shield described in claim 19 wherein said gap separating said opposing shield parts is between about 4 and 10 microns wide.
 23. A magnetic shield, comprising: a substrate on which is a first dielectric layer having a first upper surface; on said first dielectric layer, a layer of a non-magnetic material that does not fully cover said first upper surface, having a second upper surface and a thermal conductivity greater than about 300 W/m. K; on said first upper surface, a second dielectric layer that fully abuts said thermally conductive layer, having a third upper surface that is coplanar with said second upper surface; a ferromagnetic layer on said second and third upper surfaces in the form of coplanar opposing first and second magnetic shields separated by a gap; and a third dielectric layer that just fills said gap.
 24. The magnetic shield described in claim 23 wherein said thermally conductive layer of non-magnetic material is selected from the group consisting of Cu and NiCu.
 25. The magnetic shield described in claim 23 wherein said thermally conductive layer of non-magnetic material has a thickness between about 1 and 2 microns.
 26. The magnetic shield described in claim 23 wherein said gap separating said opposing shield parts is between about 4 and 10 microns wide.
 27. The process described in claim 23 wherein said ferromagnetic layer has a thickness between about 1 and 3 microns.
 28. A magnetic read/write head, comprising: a substrate on which is a first dielectric layer having a first upper surface; on said first dielectric layer, a layer of a non-magnetic material that does not fully cover said first upper surface, having a second upper surface and a thermal conductivity greater than about 300 W/m.K; on said first upper surface, a second dielectric layer that fully abuts said thermally conductive layer, having a third upper surface that is coplanar with said second upper surface; a ferromagnetic layer on said second and third upper surfaces in the form of coplanar opposing first and second magnetic shield layers separated by a gap; a third dielectric layer that just fills said gap; on said first and second magnetic shield layers, a magnetic read-head that is sandwiched between upper and lower dielectric layers; a bottom write-head shield on said upper dielectric layer; on said bottom write-head shield, a magnetic write head having a write gap; and all magnetic shields, as well as said read head and said write gap being exposed at one end of the read/write head in a plane normal to said first upper surface.
 29. The read/write head described in claim 28 wherein said thermally conductive layer of non-magnetic material is selected from the group consisting of Cu and NiCu.
 30. The read/write head described in claim 28 wherein said thermally conductive layer of non-magnetic material has a thickness between about 1 and 2 microns.
 31. The read/write head described in claim 28 wherein said gap separating said opposing shield parts is between about 4 and 10 microns wide.
 32. The read/write head described in claim 28 wherein said magnetic read head is a CIP magnetic read head.
 33. The read/write head described in claim 28 wherein said magnetic read head is a CPP magnetic read head.
 34. The read/write head described in claim 28 wherein said magnetic write head is a double planar write head.
 35. The read/write head described in claim 28 wherein said magnetic write head is a Low DC Resistance read head. 